As mobile electronic devices, such as a cell phone and a laptop personal computer, have rapidly progressed, demands are made on the batteries used as a main power source or a backup power source for the electronic devices, wherein the batteries should be increased in capacity. As such demands are increasing, non-aqueous electrolyte batteries, such as a lithium-ion secondary battery, having a high energy density, as compared to a nickel-cadmium battery and a nickel-hydrogen battery, have attracted attention.
As a representative example of an electrolytic solution for a lithium-ion secondary battery, there can be mentioned a non-aqueous electrolytic solution obtained by dissolving an electrolyte, such as LiPF6, LiBF4, LiN(CF3SO2)2, or LiCF3(CF2)3SO3, in a mixed solvent of a high permittivity solvent, such as ethylene carbonate or propylene carbonate, and a low viscosity solvent, such as dimethyl carbonate, diethyl carbonate, or ethylmethyl carbonate.
As a negative electrode active material for the lithium-ion secondary battery, a carbonaceous material capable of having occluded therein and releasing lithium ions is mainly used. Representative examples of the carbonaceous materials include natural graphite, artificial graphite, and amorphous carbon. A metal or alloy negative electrode using as a negative electrode active material, for example, silicon or tin intended to further increase the capacity has been known. On the other hand, as a positive electrode active material, a transition metal composite oxide capable of having occluded therein and releasing lithium ions is mainly used. Representative examples of transition metals in the transition metal composite oxide include cobalt, nickel, manganese, and iron.
For example, in the non-aqueous electrolyte secondary battery using the above-mentioned non-aqueous electrolytic solution, the reactivity varies depending on the composition of the non-aqueous electrolytic solution used, and therefore the battery characteristics considerably change according to the non-aqueous electrolytic solution used in the battery. For improving the non-aqueous electrolyte secondary battery in battery characteristics, such as storage characteristics, and enhancing the safety of the battery upon being overcharged, various studies have been made on the non-aqueous solvents and electrolytes used in the non-aqueous electrolytic solution.
In patent document 1, with respect to a lithium secondary battery comprising a positive electrode using a lithium-transition metal oxide, such as lithium cobalt oxide, as an active material, a negative electrode using graphite, and a non-aqueous electrolytic solution, studies are made on the improvement of the cycle characteristics by adding a malonate compound to the electrolytic solution.
In patent document 2, with respect to an electrolytic solution for an electrical double layer capacitor, studies are made on the improvement of the electrolytic solution in resistance to reduction and the suppression of leakage of a current during the constant voltage charging by adding a malonate or tricarboxylate compound to the electrolytic solution.
In patent document 3, with respect to a lithium secondary battery comprising a positive electrode using an amorphous material comprised of V2O5 or P2O5 as an active material, a negative electrode using metal lithium, and a non-aqueous electrolytic solution, studies are made on the improvement of the cycle characteristics by adding a dicarboxylic acid compound to the electrolytic solution.
In patent document 4, with respect to a lithium secondary battery comprising a positive electrode using a lithium-transition metal oxide, such as lithium cobalt oxide, as an active material, a negative electrode using artificial graphite, and a non-aqueous electrolytic solution, studies are made on the improvement of the capacity maintaining ratio after high-temperature cycles by adding a specific carboxylate compound to the electrolytic solution.